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Finding the Fourth Proportional to 642.39, 886.79 and 485.09

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Solution

The fourth proportional to 642.39, 886.79 and 485.09 is: 669.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    642.39 : 886.79 = 485.09 : x
  2. Step 2: Convert to fraction form
    642.39/886.79 = 485.09/x
  3. Step 3: Cross multiply
    642.39x = 886.79 × 485.09
  4. Step 4: Simplify right side
    642.39x = 430,172.96
  5. Step 5: Solve for x
    x = 430,172.96/642.39
  6. Step 6: Final answer
    x = 669.64

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.